Photographic materials



United States Patent Patented Apr. 4, 1967 lice 3,312,553 PHOTOGRAPHIC MATERIALS Fritz Dersch, Binghamton, N.Y., assignor to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 30, 1963, Ser. No. 319,969 8 Claims. (Cl. 96-107) The present invention relates to photographic materials of increased sensitivity and covering power which have incorporated therein a water soluble oxide adduct of gelatin.

Previously, according to heretofore customary practices, silver halide emulsions were sensitized with certain types of polyoxyalkylene glycols. Also, various derivatives of polyoxyalkylene glycols, such as the alkylene oxide adducts of glycols having from 8 to 18 carbon atoms, as well as the oxide adduct of various other active hydrogen-containing compounds such as amines,

ethers, esters and amides, have been employed to increase the sensitivity of silver halide emulsions.

However, the silver halide emulsions which were sensitized by the addition of alkylene oxide derivatives of the prior art suffered from many disadvantages which limited their use in photographic processes. Although the silver halide emulsions which had been sensitized in this manner did show a considerable increase in speed, their effectiveness was limited because of their tendency to fog during storage, particularly at elevated temperatures and humidities. Conventional antifoggants were incapable of controlling this fogging tendency and hence it was necessary to resort to special expensive antifoggants to attain this end. (See for example United States Patents 2,704,716, 2,716,062 and 2,728,666.)

Therefore, it is a primary object of this invention to provide a novel sensitized silver halide photographic emulsion, said emulsion having high photographic speed and not subject to excessive fogging during prolonged periods of storage at high humidities.

It is still another object of this invention to provide a novel sensitized silver halide emulsion which does not require the use of excessive and expensive fogging agents in order to be able to store it for relatively long periods of time.

Other objects of this invention will appear from the description of the invention.

It has now been found that the above objects can be obtained by incorporating a water-soluble polyoxyalkylene derivative of gelatin into a silver halide emulsion. While the exact structure of gelatin is not known, it occurs in bones, hides, skins, and sinews and can be readily obtained from the parent substance, collagen, by wellknown prior art treatments which usually involve some form of treatment such as degreasing in the case of bone stock, and liming or acidulation'in the case of hide and sinew stock, to prepare the raw material for the cooking step. The above treated raw material is hydrolyzed into gelatin by heating in water to yield a solution which is concentrated by vacuum evaporation and subsequently spray or drum dried to product a gelatin product recovcrable as sheets, flakes, powder, pearls or noodles depending on the mode of processing.

Any form of gelatin appears operable for the formation of the water-soluble oxide adducts thereof which are employed in the photographic materials of the invention.

The alkylene oxides which find immediate and practical applicability in producing the water-soluble polyoxyalkylene derivatives of gelatin include representative compounds such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, cyclohexene oxide with the vic epoxides being preferred.

The p-olyoxyalkylene derivatives of gelatin which are employed as sensitizers for silver halide emulsions are prepared simply by reacting gelatin with an alkylene oxide. The reaction between gelatin and an alkylene oxide is conveniently carried out simply by heating one part of gelatin with from 0.8 to 5 parts of alkylene oxide at atemperature from to 200 C. in the presence of a catalyst. The catalysts which can be employed are the alkoxides, oxides, and hydroxides of lithium, potassium, sodium, calcium, zinc. and lead. The preferred catalysts are the alkali metal hydroxides, particularly sodium hydroxide and potassium hydroxide.

The amount of water soluble polyoxyalkylene derivatives of gelatin which are incorporated into the silver halide emulsions is not narrowly critical and can vary over a wide range, depending on the amount of silver halide which is used as the sensitizer. Thus, it has been found that from .5 to 50 grams of said polyoxylene derivatives of gelatin per .4 mol of silver halide may be employed.

The polyoxyalkylene derivatives of gelatin may be incorporated into various kinds of photographic emulsions. In addition to being useful inordinary non-sensitized emulsions, they may also be used in orthochromatic, panchromatic, and X-ray emulsions. If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added. Various silver salts may be used as the sensitive salt, such as silver bromide, silver iodide, silver chloride, or mixed silver halide. The polyoxyethylene derivatives of gelatin may be used in emulsions intended for color photography, such as emulsions containing color forming agents or emulsions containing color couplers. Additionally, the dispersing agent in the photo-graphic emulsion may be gelatin or other colloids, such as collodion, albumen, cellulse derivatives i.e., carb-oxymethylcellulose, polyvinyl alcohol, polvinylpyrrolidone, or the ike. g

It has also been determined that the increase of effective sensitivity of photographic silver halide emulsions with the polyoxyalkylene derivatives of gelatin can be obtained in a number of ways. Thus they may be added to an undercoating, to a middle coating, to an overcoating or to a surface coating prior to the coating operation. Additionally, if so desired, they maybe added during the actual preparation of the emulsion either before or after Washing the emulsion.

Strangely enough, the gelatin-alkylene oxide adducts not only contribute to the photolytic properties of the silver halide emulsion, they also operate to greatly increase its covering power. This expedites coating of the emulsion on the selected base on which it is laid down. It also permits use of less silver halide than would normally be required.

The following examples will illustrate the instant invention, but it is to be understood that it is not intended that it be limited thereto.

Example I A 30% gelatin solution in water is prepared. While the temperature is held at 40 C. ethylene oxide is passed through this solution for 20 minutes. The resulting product had lower gelatin strength and the melting point dropped from 39 C. to 365 C.

Example II A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide was prepared in a conventional manner and brought up to its maximum light sensitivity. It was then readied for coating on film base by melting it at 40 C. and incorporating coating finals such as sensitizing dyes, stabilizers, and hardeners.

A 10% aqueous solution of a polyoxyethylene deriva- .tive of gelatin was prepared by reacting one part of gelatin with two parts of ethylene oxide and heating said mixture at 100 C. in the presence of sodium hydroxide. Thirty cubic centimeters of this solution was added to a sample of the above described silver halide emulsion that contained about 0.4 mole of silver halide. A sample of the same emulsion, but not containing the gelatin adduct, served as a control. The emulsion samples are then coated on a suitable cellulose ester base and dried. The film samples are exposed in a type 13 sensitometer and developed in a developer having the following composition:

Grams Metol V V 1.5 Sodium sulfite anhydrous 45.0 Sodium bisulfite 1.0 Hydroquinone 3.0 Sodium carbonate monohydrate 6.8 Potassium bromide 0.8 Water to make 1 liter.

The results obtained were as follows:

Fog

Relative Speed After 12 6 Days Dev. Oven and 4 Dev.

Quantity of Ethylene Oxide Adduct of Gelatin:

100 .10 .08 3 grams 150 .12 .09 Quantity of Polyoxyethylene Laurylether Added, 1 gram 150 .28 .16

Example III A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide was coated on a film base in a conventional manner. After the coating, an aqueous gelatin solution containing 20 grams of gelatin per liter and 30 grams of a po lyoxyethylene derivative of gelatin prepared in the same manner as disclosed in Example I was mixed and coated on the film base as an antia'brasion layer. After drying, film samples were exposed and processed as disclosed in Example H. The samples described exhibited a relative speed of 200 with a fog of .14 as compared with a type coating of the same emulsion having an antiabrasion layer similar to that described above, but lacking the speed increasing additive and having a speed of and a fog of .10.

Various modifications of the invention as set forth in the preceding examples will become evident to those skilled in the art such as the use of equivalent materials not necessarily disclosed in the specification. It is not intended, therefore, that the invention .be limited except as necessitated by the appended claims.

What is claimed is:

1. A lightsensitive silver halide emulsion sensitized with a water-soluble polyoxyalkylene derivative of gelatin resulting from the reaction of gelatin with an alkylene oxide.

2. The composition as defined in claim 1 wherein the silver halide emulsion is a silver chloride emulsion.

3. The composition as defined in claim 1 wherein the silver halide emulsion is a mixed silver bromide-silver iodide emulsion.

.4. The emulsion of claim 1 wherein the alkylene oxide is ethylene oxide.

5. The emulsion of claim 1 where the alkylene oxide is propylene oxide.

6. The emulsion of claim 1 wherein the alkylene oxide is butylene oxide.

7. The emulsion of claim 1 wherein the alkylene oxide is styrene oxide.

8. The emulsion of claim 1 wherein the alkylene oxide is cyclohexene oxide.

References Cited by the Examiner UNITED STATES PATENTS 2,380,280 7/1945 Weyerts 96-107 2,494,041 1/1950 Frame 260117 2,848,330 8/1958 Chechak et a1. 96-107 2,900,267 8/1959 Cavanau'gh et a1. '2601l7 3,047,394 7/1962 Allen et al. 96--111 3,061,436 10/1962 Himmelmann 96111 3,091,537 5/1963 Burness 96l.11

NORMAN G. TORCHIN, Primary Examiner.

A. E. TANENHOLTZ, Assistant Examiner. 

1. A LIGHT-SENSITIVE SILVER HALIDE EMULSION SENSITIZED WITH A WATER-SOLUBLE POLYOXYALKYLENE DERIVATIVE OF GELATIN RESULTING FROM THE REACTION OF GELATIN WITH AN ALKYLENE OXIDE. 